The present invention relates to a radio telephone system capable of data communication through a radio circuit, and more particularly to a radio telephone device having an interface with a data communication device, and a radio telephone system having a charger for charging a storage battery in such a radio telephone device. Description of the Related Arts
As well known in the art, radio telephone systems can be used anywhere for radio communications in areas where radio waves can be propagated, i.e., can be received by the radio telephone systems. Stated otherwise, the users of radio telephone systems can receive the benefit of telephone service anywhere insofar as radio waves can be propagated at levels high enough for radio transmission and reception irrespective of whether they are on land, at sea, or aerial.
Primary telephone service and voice/data exchange service are generally provided by way of wire telecommunication. Naturally, wire telephone service cannot be provided unless various pieces of equipment necessary for wire telecommunication, including switching exchanges, repeater exchanges, and transmission lines to subscribers, are complete. Since installation and maintenance of the necessary equipment are highly expensive, providing wire telephone service in areas where user needs are low is not cost-effective. In addition, certain geographical limitations, which may be posed by mountains, deserts, or the like, prevent necessary equipment for wire telecommunication service from being installed even if there are demands for telephone service.
Those areas which are not cost-effective for wire telephone service and which suffer from geographical limitations may be provided with telephone service by a radio telephone system. The radio telephone system can give users as good telephone service as the wire telephone system, is much less costly than the wire telephone system, and is hence highly cost-effective. Specifically, it is possible in the radio telephone system to effectively utilize frequencies and efficiently operate radio base stations by designing radio zones and selecting zone radii and transmission power settings according to the number of users of the radio telephone system and the area to be provided with the radio telephone service.
In the radio telephone system, it is sometimes desired that a data communication device be connected to a radio telephone device to carry out data communication between the radio telephone device and another data communication device through a radio circuit. Heretofore, it has been customary to provide the radio telephone device with a connector for connection to the data communication device. The connector has a physical size which may vary depending on the data interface of the data communication device to be coupled to the connector. Because of the conventional connector design, the radio telephone device, which should be portable by nature, cannot be greatly reduced in size and weight.